The present invention relates to a restraint device for occupants of a vehicle, and includes an airbag system.
It is known to accommodate airbag systems behind a protective covering, such as a dashboard cladding, door coverings, seat coverings, and the like, wherein upon deployment of the airbag the covering tears open in order to allow the airbag to pass through. In this connection, the covering must not significantly obstruct the escape of the airbag. It is still frequent practice to utilize the force of the inflating airbag in order to tear open the covering along a line of weakness, such as a tear seam or a tear filament. In this connection, the strength of the tear seam, the quality of the material, and the stretchability of the material influence the unfolding of an airbag accommodated in this fashion with great tolerance and time lag, for example from a seat back. The lines or regions of weakness can, however, not be made as weak as desired, since then the danger would exist that the covering would already open during normal intended use. Therefore, a considerable portion of the force of the inflating airbag, and the time for the opening of the covering, must be utilized, which counteracts the provision of the protective function.
It is has therefore already been proposed in U.S. Pat. No. 6,045,151 to provide the airbag system with a force concentrator for concentrating the force of the inflating or unfolding airbag onto the tear seam. This known force concentrator includes two panels of sheet material that are wound about the airbag module and that have two opposite ends that are brought together on opposite sides of the tear seam and are connected with a cover that extends over the airbag module. It is not possible to introduce the force of the airbag in a defined manner, in particular to specific locations of the tear seam.
WO 2008 095485 furthermore discloses tear strips provided on one side of a fabric section for a sleeve that surrounds the airbag; on the opposite side, the tear strips are inserted through holes or slots, and are then sewn to the tear seam. Providing insertion holes for the strips increases the manufacturing and assembly cost and effort, and reduces the opening force of the airbag.
It is an object of the present invention to provide a restraint device of the aforementioned general type that simplifies manufacture and assembly of the airbag system, and directs the expanding or unfolding airbag in a more effective and defined manner onto the tear seam.